Measurement Computing WavePort 312P rev.1.0 - Manual (Page 66)

8-2 Cycle-by-Cycle Capture PowerVista/312 User’s Manual
• Update Rate: is the rate at which the Cycle-by-Cycle graphic windows are updated. Note that as data
is updated, the entire curve is plotted. Thus, the Window Size and Update Rate are key factors in the
processing performance. If FIFO overruns are generated, slow the update rate by setting the Update
Rate time higher, say to 2 or 3 seconds. If overruns continue, consider minimizing one or both of the
Result Windows, or resizing them smaller so that less window area is needed for plotting.
• Link Time Scale on Plots: when checked will link Plot 1 and Plot 2 so that when any panning or
zooming is performed, the alternate partner plot will follow the scaling. This is a horizontal axis link
only.
• Auto Snap to Database on Full Window: allows a full window of captured data to be automatically
snapped to the database before beginning a subsequent capture. This feature is accomplished with no
loss of data. At 226 kBytes per 3600 point window and 400 Megabytes of disk space, Cycle-by-Cycle
capture could continuously capture data at 60 Hz for about 30 hours. See the Scrolling Data and Auto
Snap to Database application for more information.
• Window Size: is the size of the scrolling window in cycles. While data is collected, if the total number
of points collected at any time is less than the Window Size, then only those points are plotted. As the
number of points grows to the Window Size, the plotted curves will appear to compress as more and
more data is plotted within the Result Window. When the Window Size is reached, the data plotted will
scroll from right to left. Data scrolled off the left end is lost, unless the Auto Snap to Database on Full
Window option is checked.. See the Scrolling Data and Auto Snap to Database application for more
information.
8.3 Cycle-by-Cycle Application
Cycle-by-Cycle acquisition is used to measure the detailed, but not sub-cycle, response of power equipment.
Each cycle measured is processed into RMS volts, amps, watts, vars, and frequency (if Frequency Following is
enabled). The results are plotted for users during data capture for immediate feedback and decision making.
The efficiency and speed of data saving within EasyPower Measure make the need for specialty triggering
during Cycle-by-Cycle data capture unnecessary. The user can simply start the acquisition, record continuously,
and wait for all desired disturbance or tests to occur. As noted in the Cycle-by-Cycle Configuration, 400
Mbytes of disk space for 60 Hz will result in 30 hours of continuous cycle-by-cycle data recording of all signals.
Several application examples are discussed below.
8.3.1 Scrolling Data and Auto Snap to Database
As noted in the Window Size description under Cycle-by-Cycle Configuration, as more points are gathered, the
Result Window plot appears to compress as more and more points are plotted. When the Window Size is
reached, the Result Window scrolls from right to left. Data scrolled off the left end is lost unless the Auto Snap
to Database feature in checked.
If the Auto Snap to Database feature is checked, then when the Window size is reached, EasyPower Measure
automatically snaps the full Window Size of data into the database. A description line is added to the shot list,
and the number of events will increment by one. The description line will include an additional "- AutoX" text
note at the end, where X is a number beginning at 1 and incrementing by one upward for each shot until the
Auto Snap session is terminated. In this way, an Auto Snap session is clearly marked in the database.
As data is continuing to be collected, the Result Window will scroll left. Note that the Result Window is not
cleared and restarted each time an automatic snap of data is performed. The acquisition has been designed this
way so that the user always has the latest minute of information within view. This gives the display complete
continuity as data is collected.